Hall, Richard P. 1900-1969. Protozoa; the simplest of all animals / Richard P. Hall. - New York : Holt, Rinehart and Winston, c1964 - 123 p. : ill. ; 21 cm. - Holt library of science ; ser. 2, v. 22 . - Holt library of science ; ser. 2, v. 22. . Bibliography: p. 111. Subjects--Topical Terms: Protozoology. Dewey Class. No.: 579.4 / HAP 1964